TECH TIP
F-150 A/C Inoperative – DTC B1B71:11
Aug. 07 2021
Aug. 07 2021

Vehicle: 2013 F-150, 4WD, V6-3.5L Turbo, Automatic Transmission

Mileage: 148,090

Problem: The A/C stopped working on this Ford F-150 so the customer brought it to the shop.
NOTE: The vehicle was equipped with an electronic automatic temperature control (EATC) system.

Case Details: The technician connected A/C gauges and found that the system was full of refrigerant. Next, he scanned all modules for diagnostic trouble codes (DTCs) and discovered a laundry list of DTCs from multiple modules. After he cleared the codes, only one returned:

B1B71:11 - Evaporator Temperature Sensor Circuit Short to Ground 

F-150 AC Diagram

 

Looking at the evaporator temperature sensor parameter identification data (PID) on the scan tool, the technician noticed it was reporting, -40°F. At this point, the technician called an ALLDATA Tech-Assist consultant for some guidance.


    The consultant advised using the wiring diagram as a guide to verify circuit integrity at the evaporator temperature sensor. If the circuits checked out good, he said to attach a jumper wire between the two terminals and watch the PID. If it jumped up to the maximum temperature value (+140°F), the EATC control module was okay; the sensor was faulty. If the PID value remained at -40°F, the EATC control module had likely failed.

    The technician followed the Tech-Assist consultant’s diagnostic advice and found circuit VH406 (VT wire) from the EATC control module to the evaporator temperature sensor had broken near connector C263.

    Confirmed Repair: He repaired the wiring and cleared the DTC. The evaporator temperature sensor PID began reporting accurately, the DTC did not return, and the A/C operated as designed. Fixed!

     

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